Family and familiarity in flies

Thesis

The concept of gene-centred evolution and subsequent inclusive fitness theory provided a formal framework in which to study the adaptation of social behaviours. It highlighted the role of relatedness between individuals in mediating both cooperation and conflict. However, social behaviours can be difficult to study, particularly among animals in the wild. Drosophila melanogaster has been studied as a model organism for over a century, and we have a deep understanding of its genetics, development and physiology. Furthermore, its short lifespan, small size and fast reproduction rate make it an ideal laboratory animal. Yet we currently know very little about how relatedness affects social behaviours in this species. In this thesis, I aim to contribute to our knowledge of kin selection and recognition in Drosophila melanogaster, developing its use as a model organism for studying inclusive fitness.

In Chapter 2, I examine the role of relatedness on adult sexual behaviours, namely how male-male relatedness mediates sexual harm to females. I distinguish the roles of genetic relatedness and larval social familiarity, and find that familiarity alone is not sufficient and genetic relatedness is required to reduce sexual conflict. However, male intrasexual interactions are important, as in Chapter 3, I find no effect of relatedness when males are presented to the female sequentially rather than simultaneously.

In Chapters 4 and 5, I consider the effect of relatedness on larval social behaviours, which have thus far been understudied compared to their adult counterparts. Contrary to predictions from inclusive fitness theory, in Chapter 4 I find that larvae benefit from developing in unrelated, rather than related, groups. This is possibly due to the increased genetic diversity and therefore behavioural diversity in unrelated groups, reducing direct competition. In Chapter 5, I additionally show that larvae prefer to cannibalise unrelated and unfamiliar conspecific victims, which may have strong fitness consequences for both adult and larval behaviour.

This thesis provides new evidence that relatedness, over and above social familiarity, mediates both adult and larval behaviours in Drosophila melanogaster, allowing us further to develop this species as a model organism for kin selection.

Authors: Le Page, S

• DOI: 10.5287/ora-d58qmqmrw
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: Kin selection; Kin discrimination; Drosophila melanogaster; Sexual conflict
• Subjects: Zoology; Evolution (Biology); Behavioural Ecology